Previous clinical observations have suggested that with increased age, decremental changes in salivary gland function occur. To study the mechanism of this alteration in animal models, salivary glands from young adult and aged male and female rats have been characterized biochemically and their regulation by neurotransmitters has been investigated. Included are studies of: (1) protein secretion from ther parotid gland and its relationship to beta-adrenergic stimulated endogenous protein phosphorylation; and (2) fluid and electrolyte section (K efflux, Ca efflux, alpha-adrenergic and cholinergic responsiveness) from the parotid gland. In the submanibular gland, basal protein biosynthesis and release has been characterized. The role of both alpha- and beta-adrenergic receptor stimulation in maximum exocrine protein secretion form the submandibular gland has been evaluated.